Refrigeration systems typically include a compressor, an evaporator, an evaporator fan, an expansion device, a condenser, and a condenser fan which operate together to cool a refrigerated space. The compressor, expansion device, condenser, and evaporator are fluidly coupled such that a loop or a closed system exists for circulation of a refrigerant therein. The compressor receives the refrigerant in a gaseous form from the evaporator and pressurizes the gas such that the gas changes from the gaseous state into a liquid state as it unloads heat to an air stream moving through the condenser. Once the refrigerant reaches the liquid state in the condenser, the refrigerant is sent through an expansion device before reaching the evaporator, which is held at a low pressure by the operation of the expansion device and compressor. The low pressure of the evaporator causes the refrigerant to change state back to a gas and, as it does so, to absorb heat from an air stream moving through the evaporator. In this manner, the air stream flowing through the evaporator is cooled and the temperature of the refrigerated space is lowered.
The evaporator fan is typically disposed proximate the evaporator and is operable to generate a flow of air through the evaporator and into a refrigerated space. An air flow through the evaporator is cooled as a liquid refrigerant passes therethrough. In this regard, the air flow may be regulated to control the temperature of the exiting air stream and the overall temperature of the refrigerated space.
A bank of parallel condensing units may be used in conjunction with a bank of evaporators to cool a plurality of refrigerated spaces. Each condensing unit includes one or more compressors fluidly coupled to the bank of evaporator units, whereby the evaporator units are disposed within a building generally proximate a refrigerated space and the condensing units are disposed outside of the building and are operable to expel heat absorbed by the evaporators. Having the condensing units in fluid communication with the evaporator units provides the refrigeration system with flexibility as each condensing unit may be independently activated to provide a desired amount of liquid refrigerant to each of the evaporator units, thereby evenly controlling the cooling of each refrigerated space.
Conventionally, the condensing units operate independently according to local set points. The conventional system, however, results in certain inefficiencies. For example, compressors on each of the condensing units may be activated and deactivated independent of condenser capacity across the bank of condensing units. In such case, one condensing unit may be operating at or near maximum compressor capacity while a parallel condensing unit may be operating at or near minimum compressor capacity.